In a process of mounting a semiconductor element, the semiconductor element and a substrate are bonded together with a bonding material. For example, a next-generation power semiconductor element (for example, a silicon carbide semiconductor, or a gallium nitride semiconductor) is used as the semiconductor element. Patent Literature 1 discloses a method for laminating a semiconductor element and a substrate with a bonding material therebetween and then sintering the semiconductor element and the substrate in a heating furnace to bond the two together.